Abstract

We study the asymptotic behaviour of random walks in i.i.d. non-elliptic random environments on $\mathbb{Z} ^d$. Standard conditions for ballisticity and the central limit theorem require ellipticity, and are typically non-local. We use oriented percolation and martingale arguments to find non-trivial local conditions for ballisticity and an annealed invariance principle in the non-elliptic setting. The use of percolation allows certain non-elliptic models to be treated even though ballisticity has not been proved for elliptic perturbations of these models.

Highlights

  • A central topic in modern probability and statistical physics is the study of random walks in random media

  • Existing results have largely been restricted to situations where the random environment is elliptic, i.e. where steps to all nearest neighbours are possible

  • Random walks in i.i.d. random environments are not reversible

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Summary

Introduction

A central topic in modern probability and statistical physics is the study of random walks in random media. We will study random walks in i.i.d. random environments (RWRE) that are non-elliptic, such as in the following example. Dimensional-orthant model (Example 1) is the uniform RWRE on the random directed graph which has Gx = ←↓ with probability 1 − p. In many settings we will be able to conclude that the range of the walker satisfies condition (b) of the theorem by proving that it holds for the range of such a transverse walk. We will find that in Example 1, having strong barriers ←↓ is an insurmountable obstacle to obtaining a positive speed in direction l = (1, 1) using one of the standard ballisticity conditions. One way of interpreting our results in the context of Example 1 is that we can overcome the presence of strong barriers ←↓ by strengthening the forward push and including sufficiently many sites ↑→ that don’t permit backwards motion

Regeneration and Ballisticity
Proof of Theorem 1
Proof of Proposition 3
Proof of Proposition 2
Ballisticity in the elliptic case
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